LEDs, as newly emerged solid light sources, have the prospect of becoming a new generation of light source with advantages such as energy conservation, environmental protection, long service life and the like. It is known that an LED is driven by a DC voltage. However, AC power is generally supplied in daily life. Therefore, for the LED to normally emit light, a power converter is required to implement the functions of rectification and voltage reduction. Introduction of a power converter may bring about many negative effects. Firstly, service life of the power converter is far shorter than that of the LED, so service life of a light-emitting device may be shortened. Secondly, the power converter may reduce efficiency of the light-emitting device. Thirdly, in a low-power application, the power converter may cause reduction of the power factor and increase of the total harmonic current. In order to fully utilize the advantages of the LED, an LED light-emitting device directly driven by an AC power is developed.
In conventional technical solutions of LED driving, in combination with a traditional silicon-controlled dimmer, only the traditional function of luminance adjustment is considered, but the adjustability of color temperature and hue of the LED is not taken into consideration. In addition, in most of the conventional technical solutions of LEDs driven by the AC power, multiple LED components are coupled in reverse parallel or based on a topology of a rectification bridge circuit, to meet the driving requirements of the AC power. However, the AC power is subjected to fluctuation according to a specific frequency cycle. Since the LED has its own switch-on voltage, when the transient voltage exceeds the switch-on voltage, the LED may be unintentionally switched on and emit light. Otherwise, the LED may be cut-off and does not emit light. Such circuit causes low light-emitting efficiency for the LED, and in addition, when the AC voltage fluctuates, the LED may flicker.